Proteins, peptides and other biological molecules (“biological macromolecules”, namely biological polymers such as proteins and polypeptides) are increasingly being use in many diverse areas of science and technology. For example, proteins are employed as active agents in the fields of pharmaceuticals, vaccines and veterinary products. Unfortunately, the use of biological macromolecules as active agents in pharmaceutical compositions is often severely limited by the presence of natural barriers of passage to the location where the active agent is required. Such barriers include the skin, lipid bi-layers, mucosal membranes, severe pH conditions and digestive enzymes.
There are many obstacles to successful oral delivery of biological macromolecules. For example, biological macromolecules are large and are amphipathic in nature. More importantly, the active conformation of many biological macromolecules may be sensitive to a variety of environmental factors, such as temperature, oxidizing agents, pH, freezing, shaking and shear stress. In planning oral delivery systems comprising biological macromolecules as an active agent for drug development, these complex structural and stability factors must be considered. In addition, in general, for medical and therapeutic applications, where a biological macromolecule is being administered to a patient and is expected to perform its physiologic action, delivery vehicles can be used to facilitate absorption through the gastro-intestinal tract. These delivery vehicles must be able to release active molecules at a rate that is consistent with the needs of the particular patient or the disease process.
One specific biological macromolecule, the hormone insulin, contributes to the normal regulation of blood glucose levels through its release by the pancreas, more specifically by the β-cells of a major type of pancreatic tissue (the islets of Langerhans), so that the glucose can be used as a source of energy. Insulin secretion is a regulated process that, in normal subjects, provides stable concentrations of glucose in blood during both fasting and feeding. In healthy humans, insulin is secreted from the pancreas into the portal vein, which carries the insulin to the liver. The liver utilizes and/or metabolizes a large portion of the insulin that it receives from the portal circulation. In very basic terms, the liver plays a key role in the metabolism of glucose as follows: in the presence of excess insulin, excess glucose, or both, the liver modulates the production of glucose released into the blood; and, in the absence of insulin or when the blood glucose concentration falls very low, the liver manufactures glucose from glycogen and releases it into the blood. The liver acts as a key blood glucose buffer mechanism by keeping blood glucose concentrations from rising too high or from falling too low.
Blood glucose concentration is the principal stimulus to insulin secretion in healthy humans. The exact mechanism by which insulin release from the pancreas is stimulated by increased glucose levels is not fully understood, but the entry of glucose into the β-cells of the pancreas is required. Glucose enters the pancreatic β-cells by facilitated transport and is then phosphorylated by glucokinase. Expression of glucokinase is primarily limited to cells and tissues involved in the regulation of glucose metabolism, such as the liver and the pancreatic β-cells. The capacity of sugars to undergo phosphorylation and subsequent glycolysis correlates closely with their ability to stimulate insulin release. It is noted that not all tissues are dependent on insulin for glucose uptake. For example, the brain, kidneys and red blood cells are insulin independent tissues, while the liver, adipose and muscle are insulin dependent tissues.
When evoked by the presence of glucose (e.g., after a solid meal is ingested) in a non-diabetic individual, insulin secretion is biphasic: shortly after ingesting food, the pancreas releases the stored insulin in a burst, called a first phase insulin response, and then approximately 15-20 minutes later outputs further insulin to control the glycemic level from the food. The first phase insulin response reaches a peak after 1 to 2 minutes and is short-lived, whereas a second phase of secretion has a delayed onset but a longer duration. Thus, secretion of insulin rises rapidly in normal human subjects as the concentration of blood glucose rises above base levels (e.g., 100 mg/100 ml of blood), and the turn-off of insulin secretion is also rapid, occurring within minutes after reduction in blood glucose concentrations back to the fasting level.
In healthy human subjects, insulin secretion is a tightly regulated process that maintains blood concentrations of glucose within an acceptable range regardless of whether or not the subject has ingested a meal (i.e., fasting and fed states). Insulin facilitates (and increases the rate of) glucose transport through the membranes of many cells of the body, particularly skeletal muscle and adipose tissue. Insulin has three basic effects: the enhanced rate of glucose metabolism, the promotion of increased glycogen stores in muscle and adipose tissue, and decreased circulating blood glucose concentration.
Diabetes Mellitus (“diabetes”) is a disease state in which the pancreas does not release insulin at levels capable of controlling blood glucose and/or in which muscle, fat and liver cells respond poorly to normal insulin levels because of insulin resistance. Diabetes thus can result from a dual defect of insulin resistance and “burn out” of the β-cells of the pancreas. Diabetes is classified into two types: Type 1 and Type 2. Approximately 5 to 10% of diagnosed cases of diabetes are attributed to Type 1, and approximately 90% to 95% are attributed to Type 2.
Type 1 diabetes is diabetes that is insulin dependent and usually first appears in young people. In Type 1 diabetes, the islet cells of the pancreas stop producing insulin mainly due to autoimmune destruction, and the patient must self-inject the missing hormone. For type 1 diabetics, insulin therapy is essential and is intended to replace the absent endogenous insulin with an exogenous insulin supply.
Type 2 diabetes is commonly referred to as adult-onset diabetes or non-insulin dependent diabetes and may be caused by a combination of insulin resistance (or decreased insulin sensitivity) and, in later stages, insufficient insulin secretion. This is the most common type of diabetes in the Western world. Close to 6% of the adult population of various countries around the world, including the United States, have Type 2 diabetes, and about 30% of these patients will need exogenous insulin at some point during their lifespans due to secondary pancreatic exhaustion and the eventual cessation of insulin production. For type 2 diabetics, therapy has consisted first of oral antidiabetic agents, which increase insulin sensitivity and/or insulin secretion, and only then insulin if, and when, the oral agents fail.
Diabetes is the sixth leading cause of death in the United States and accounted for more than 193,000 deaths in 1997. However, this figure is an underestimate because complications resulting from diabetes are a major cause of morbidity in the population. Diabetes is associated with considerable morbidity and mortality in the form of cardiovascular disease, stroke, digestive diseases, infection, metabolic complications, ophthalmic disorders, neuropathy, kidney disease and failure, peripheral vascular disease, ulcerations and amputations, oral complications, and depression. Thus, diabetes contributes to many deaths that are ultimately ascribed to other causes.
The main cause of mortality with Diabetes Mellitus is long term micro- and macro-vascular disease. Cardiovascular disease is responsible for up to 80% of the deaths of type 2 diabetic patients, and diabetics have a two- to four-fold increase in the risk of coronary artery disease, equal that of patients who have survived a stroke or myocardial infarction. In other words, heart disease, high blood pressure, heart attacks and strokes occur two to four times more frequently in adult diabetics than in adult non-diabetics. This increased risk of coronary artery disease combined with an increase in hypertensive cardiomyopathy manifests itself in an increase in the risk of congestive heart failure. These vascular complications lead to neuropathies, retinopathies and peripheral vascular disease. Diabetic retinopathy (lesions in the small blood vessels and capillaries supplying the retina of the eye, i.e., the breakdown of the lining at the back of the eye) is the leading cause of blindness in adults aged 20 through 74 years, and diabetic kidney disease, e.g., nephropathy (lesions in the small blood vessels and capillaries supplying the kidney, which may lead to kidney disease, and the inability of the kidney to properly filter body toxins), accounts for 40% of all new cases of end-stage renal disease (kidney failure). Furthermore, diabetes is also the leading cause for amputation of limbs in the United States. Diabetes causes special problems during pregnancy, and the rate of congenital malformations can be five times higher in the children of women with diabetes.
Poor glycemic control contributes to the high incidence of these complications, and the beneficial effects of tight glycemic control on the chronic complications of diabetes are widely accepted in clinical practice. However, only recently has it been firmly established that elevated blood glucose levels are a direct cause of long-term complications of diabetes. The Diabetes Control and Complications Trial and the United Kingdom Prospective Diabetes Study both showed that control of blood glucose at levels as close to normal as possible prevents and retards development of diabetic retinopathy, nephropathy, neuropathy and microvascular disease.
Insulin resistance (or decreased insulin sensitivity) is also prevalent in the population, especially in overweight individuals, in those with risk of diabetes (i.e., pre-diabetic, wherein blood glucose levels are higher than normal but not yet high enough to be diagnosed as diabetes) and in individuals with type 2 diabetes who produce enough insulin but whose tissues have a diminished ability to adequately respond to the action of insulin. When the liver becomes insulin-resistant, the mechanism by which insulin affects the liver to suppress its glucose production breaks down, and the liver continues to produce glucose, even under hyperinsulinemic conditions (elevated plasma insulin levels). This lack of suppression can lead to a hyperglycemia (elevated blood glucose levels), even in a fasting state.
In order to compensate and to overcome the insulin resistance, the pancreatic β-cells initially increase their insulin production such that insulin resistant individuals often have high plasma insulin levels. This insulin is released into the portal vein and presented to the liver constantly or almost constantly. It is believed that the liver's constant exposure to high levels of insulin plays a role in increased insulin resistance and impaired glucose tolerance. After a period of high demand placed on the pancreatic β-cells, the cells start to decompensate and exhaust, and insulin secretion, or insulin secretory capacity, is reduced at later stages of diabetes. It is estimated that, by the time an individual is diagnosed with type 2 diabetes, roughly 50% of the β-cells have already died due to increased demand for insulin production.
Insulin resistance plays an important role in the pathogenesis of hyperglycemia in type 2 diabetes, eventually inducing the development of diabetic complications. Furthermore, insulin resistance ostensibly plays a role in the pathogenesis of macrovascular disease, cardiovascular diseases and microvascular disease. See, for example, Shinohara K. et al., Insulin Resistance as an Independent Predictor of Cardiovascular Mortality in Patients With End-Stage Renal Disease, J. Am. Soc. Nephrol., Vol. 13, No. 7, July 2002, pp. 1894-1900. Research currently shows that insulin resistance reaches a maximum and then plateaus. Once the insulin resistance plateaus, it is believed to not get appreciably worse, but can improve.
Diabetes or insulin resistance can be diagnosed in many ways, as is known to those in the art. For example, the initial diagnose may be made from a glucose tolerance test (GTT), where a patient is given a bolus of glucose, usually orally, and then the patient's blood glucose levels are measured at regular time intervals for approximately 2 hours, or as many as 6 hours in the case of an extended GTT. Another method of testing for diabetes or insulin resistance is a test of the patients fasting or postprandial glucose. Other tests, such as Glycosolated Hemoglobin, often reported as Hemoglobin A1c (HbA1c) can be used to assess blood glucose over 2-3 months.
Several methods to assess insulin resistance are currently available, including the euglycemic-hyperinsulinemic clamp, fasting plasma insulin, homeostasis model assessment (HOMA) of insulin resistance (HOMA-IR), the fasting glucose-to-insulin ratio method and quantitative insulin sensitivity check index (QUICKI). Except for the euglycemic-hyperinsulinemic clamp method, the others are surrogate indices and are indirect methods of assessing insulin resistance. For example, the HOMA-IR is calculated from fasting plasma glucose (FPG) and fasting immunoreactive insulin (FIRI) with the formula HOMA-IR=FIRI in mU/l×FPG in mg/dl/405. In addition, the reciprocal index of homeostasis model assessment (1/HOMA-IR) is also calculated. Similarly, QUICKI is derived from logarithmic-transformed FPG and insulin levels as calculated from FPG and FIRI levels with the formula QUICKI=1/(log [FIRI in mU/l]+log [FPG in mg/dl]).
Several oral hypoglycemic agents have been developed for specifically improving a patient's insulin resistance, such as thiazolidinediones, which make the patient more sensitive to insulin, and biguanides, which decrease the amount of glucose made by the liver, and these are currently available clinically for patients with diabetes and insulin resistance. In addition, sulfonylureas stimulate the pancreas to make more insulin, alpha-glucosidase inhibitors slow the absorption of the starches eaten by an individual, meglitinides stimulate the pancreas to make more insulin, and D-phenylalanine derivatives help the pancreas make more insulin quickly. Present treatment of insulin resistance involves sensible lifestyle changes, including weight loss to attain healthy body weight, 30 minutes of accumulated moderate-intensity physical activity per day and diet control, including increased dietary fiber intake and regulation of blood sugar levels and of caloric intake. In addition, Metformin, which has been used successfully for some time to treat diabetes because it increases insulin sensitivity, is also being studied as a treatment.
The aim of insulin treatment of diabetics is typically to administer enough insulin such that the patient will have normal carbohydrate metabolism throughout the day. Because the pancreas of a diabetic individual does not secrete sufficient insulin throughout the day, in order to effectively control diabetes through insulin therapy, a long-lasting insulin treatment, known as basal insulin, must be administered to provide the slow and steady release of insulin that is needed to control blood glucose concentrations and to keep cells supplied with energy when no food is being digested. Basal insulin is necessary to suppress glucose production between meals and overnight, and preferably mimics the patient's normal pancreatic basal insulin secretion over a 24-hour period. Thus, a diabetic patient may administer a single dose of a long-acting insulin each day subcutaneously, with an action lasting about 24 hours.
Furthermore, in order to effectively control diabetes through insulin therapy by dealing with post-prandial rises in glucose levels, a bolus, fast-acting treatment must also be administered. The bolus insulin, which has generally been administered subcutaneously, provides a rise in plasma insulin levels at approximately 1 hour after administration, thereby limiting hyperglycemia after meals. Thus, these additional quantities of regular insulin, with a duration of action of, e.g., 5-6 hours, may be subcutaneously administered at those times of the day when the patient's blood glucose level tends to rise too high, such as at meal times. Alternative to administering basal insulin in combination with bolus insulin, repeated and regular lower doses of bolus insulin may be administered in place of the long-acting basal insulin, and bolus insulin may be administered postprandially as needed.
The problem of providing bioavailable unmodified human insulin, in a useful form, to an ever-increasing population of diabetics has occupied physicians and scientists for almost 100 years. Many attempts have been made to solve some of the problems of stability and biological delivery of this peptide. Because insulin is a peptide drug (MW approx. 6000 Da) that is not absorbed intact in the gastrointestinal tract, it ordinarily requires parenteral administration such as by subcutaneous injection. Thus, most diabetic patients self-administer insulin by subcutaneous injections, often multiple times per day. However, the limitations of multiple daily injections, such as pain, inconvenience, frequent blood glucose monitoring, poor patient acceptability, compliance and the difficulty of matching postprandial insulin availability to postprandial glucose-control requirements, are some of the shortcomings of insulin therapy.
Currently, regular subcutaneously injected insulin is recommended to be dosed at 30 to 45 minutes prior to mealtime. As a result, diabetic patients and other insulin users must engage in considerable planning of their meals and of their insulin administrations relative to their meals. Unfortunately, intervening events that may take place between administration of insulin and ingestion of the meal may affect the anticipated glucose excursion. Furthermore, there is also the potential for hypoglycemia if the administered insulin provides a therapeutic effect over too great a time, e.g., after the rise in glucose levels that occur as a result of ingestion of the meal has already been lowered.
Despite studies demonstrating the beneficial effects of tight glycemic control on chronic complications of diabetes, clinicians do not often recommend aggressive insulin therapy, particularly in the early stages of the disease, and this is widely accepted in clinical practice. The unmet challenge of achieving tight glycemic control is due, in part, to the shortcomings of frequent blood glucose monitoring, the available subcutaneous route of insulin administration and the fear of hypoglycemia. In addition to the practical limitations of multiple daily injections discussed above, the shortcomings of the commonly available subcutaneous route of insulin administration have resulted in the generally inadequate glycemic control believed to be associated with many of the chronic complications (comorbidities) associated with diabetes. Thus, while intensive insulin therapy may reduce many of the complications of diabetes, the treatment also increases the risk of hypoglycemia and often results in weight gain, as reported in Diabetes Care, Volume 24, pp. 1711-21 (2001).
In addition, hyperinsulinemia (elevated blood concentrations of insulin) can also occur, such as by the administration of insulin in a location (and manner) that is not consistent with the normal physiological route of delivery. Insulin circulates in blood as the free monomer, and its volume of distribution approximates the volume of extracellular fluid. Under fasting conditions, the concentration of insulin in portal blood is, e.g., about 2-4 ng/mL, whereas the systemic (peripheral) concentration of insulin is, e.g., about 0.5 ng/mL, in normal healthy humans, translating into, e.g., a 5:1 ratio. In human diabetics who receive insulin via subcutaneous injection, the portal vein to periphery ratio is changed to about 0.75:1. Thus, in such diabetic patients, the liver does not receive the necessary concentrations of insulin to adequately control blood glucose, while the peripheral circulation is subjected to higher concentrations of insulin than are found in healthy subjects. Elevated systemic levels of insulin may lead to increased glucose uptake, glycogen synthesis, glycolysis, fatty acid synthesis, cortisol synthesis and triacylglycerol synthesis, leading to the expression of key genes that result in greater utilization of glucose.
One aspect of the physiological response to the presence of insulin is the stimulation of glucose transport into muscle and adipose tissue. It has been reported that hyperglycemia and/or hyperinsulinemia is related to vascular diseases associated with diabetes. Impairment to the vascular system is believed to be the reason behind conditions such as microvascular complications or diseases, such as retinopathy, neuropathy (impairment of the function of the autonomic nerves, leading to abnormalities in the function of the gastrointestinal tract and bladder and loss of feeling in lower extremities) and nephropathy, or macrovascular complications or diseases, such as cardiovascular disease, etc.
In the field of insulin delivery, where multiple repeated administrations are required on a daily basis throughout the patient's life, it is desirable to create compositions of insulin that do not alter physiological clinical activity and that do not require injections. Oral delivery of insulin is a particularly desirable route of administration, for safety and convenience considerations, because it can minimize or eliminate the discomfort that often attends repeated hypodermic injections. It has been a significant unmet goal in the art to imitate normal insulin levels in the portal and systemic circulation via oral administration of insulin.
Oral delivery of insulin may have advantages beyond convenience, acceptance and compliance issues. Insulin absorbed in the gastrointestinal tract is thought to mimic the physiologic route of insulin secreted by the pancreas because both are released into the portal vein and carried directly to the liver before being delivered into the peripheral circulation. Absorption into the portal vein maintains a peripheral-portal insulin gradient that regulates insulin secretion. In its first passage through the liver, roughly 60% of the insulin is retained and metabolized, thereby reducing the incidence of peripheral hyperinsulinemia, a factor linked to complications in diabetes.
However, insulin exemplifies the problems confronted in the art in designing an effective oral drug delivery system for biological macromolecules. Insulin absorption in the gastrointestinal tract is prevented presumably by its molecular size and its susceptibility for enzymatic degradation. The physicochemical properties of insulin and its susceptibility to enzymatic digestion have precluded the design of a commercially viable oral or alternate delivery system.
Emisphere Technologies, Inc. has developed compositions of insulin that are orally administrable, e.g., absorbed from the gastrointestinal tract in adequate concentrations, such that the insulin is bioavailable and bioactive following oral administration and provide sufficient absorption and pharmacokinetic/pharmacodynamic properties to provide the desired therapeutic effect, i.e., cause a reduction of blood glucose, as disclosed in U.S. Patent Applications Nos. 10/237,138, 60/346,746, 60/347,312, 60/368,617, 60/374,979, 60/389,364, 60/438,195, 60/438,451, 60/578,967, 60/452,660, 60/488,465, 60/518,168, 60/535,091 and 60/540,462, as well as in International Patent Application Publications Nos. WO 03/057170, WO 03/057650 and WO 02/02509 and International Patent Application No. PCT/US04/00273, all assigned to Emisphere Technologies, Inc., all of which are incorporated herein by reference.
The novel drug delivery technology of Emisphere Technologies, Inc. is based upon the design and synthesis of low molecular weight compounds called “delivery agents.” When formulated with insulin, the delivery agent, which is in a preferred embodiment sodium N-[4-(4-chloro-2 hydroxybenzoyl)amino]butyrate (4-CNAB), enables the gastrointestinal absorption of insulin. It is believed that the mechanism of this process is that 4-CNAB interacts with insulin non-covalently, creating more favorable physical-chemical properties for absorption. Once across the gastrointestinal wall, insulin disassociates rapidly from 4-CNAB and reverts to its normal, pharmacologically active state. 4-CNAB is not intended to possess any inherent pharmacological activity and serves only to increase the oral bioavailability of insulin by facilitating the transport of insulin across the gastrointestinal wall. The pharmacology of insulin is the desired therapeutic effect and is well characterized.
Insulin/4-CNAB capsules were evaluated by Emisphere Technologies, Inc. in a nonclinical program that included pharmacological screening, pharmacokinetic and metabolic profiles, and toxicity assessments in rats and monkeys. These studies in rats and monkeys showed that 4-CNAB is absorbed rapidly following oral administration and that, over the range tested, insulin absorption increased with increasing doses of 4-CNAB. Similarly, for a fixed oral dose of 4-CNAB, insulin absorption increased with increasing doses of insulin. Preclinical pharmacokinetic studies in rats and monkeys showed that both insulin and 4-CNAB were absorbed and eliminated rapidly following oral administration. Receptor binding screening assays revealed that 4-CNAB possessed no inherent pharmacological activity and serves only to facilitate the oral bioavailability of insulin.
Toxicology studies were also conducted in rats and monkeys to assess the potential toxicity of 4-CNAB, alone or in combination with insulin. Based on the 14-day oral repeated dose toxicity studies, the NOAEL (No-Adverse Effect Level) was estimated to be 500 mg/kg in Sprague-Dawley rats, and 400 mg/kg in rhesus monkeys. In the 90-day oral repeated dose toxicity studies, NOAELs of 250 mg/kg and 600 mg/kg were observed in rats and monkeys, respectively. Four genotoxicity studies have also been conducted with 4-CNAB, with no positive findings. Developmental and reproductive toxicology studies have not yet been conducted.
Oral insulin/4-CNAB capsules were also evaluated by Emisphere Technologies, Inc. in clinical human studies for safety, pharmacokinetics, pharmacodynamics, and the effect of food on the absorption of insulin/4-CNAB. In these studies, 4-CNAB was shown to enhance the gastrointestinal absorption of insulin following oral administration in diabetic patients and healthy subjects. Oral administration of Insulin/4-CNAB capsules resulted in rapid absorption (tmax˜20-30 minutes) of both insulin and 4-CNAB, and the insulin absorbed orally in combination with 4-CNAB was pharmacologically active, as demonstrated by a reduction of blood glucose in healthy and diabetic subjects and by a blunting of postprandial glucose excursion in diabetic patients. These studies suggest that oral administration of a formulation of insulin/4-CNAB is well-tolerated and reduces blood glucose concentrations in both healthy subjects and diabetic patients.
Whereas traditional subcutaneous insulin dosing shifts the point of entry of insulin into the systemic circulation from the natural site (the portal vein), the oral dosing method developed by Emisphere Technologies, Inc. is thought to mimic natural physiology, namely, the ratio of concentration of insulin in the portal circulation to that in the systemic circulation approaches the normal physiological ratio, e.g., from about 2:1 to about 6:1. The effect of this route of dosing is two fold. First, by targeting the liver directly, a greater control of glucose may be achieved. Various studies have shown that intraportal delivery of insulin can yield a comparable control of glucose at infusion rates lower than those required by peripheral administration. Because the orally-administered insulin will undergo substantial (˜50%) first-pass metabolism prior to entering the systemic circulation, a lower plasma concentration and total exposure is achieved compared to an subcutaneous equivalent dose. This may, in turn, alleviate any detrimental effects of insulin on non-target tissues.
Thus, the oral insulin formulations of Emisphere Technologies, Inc. provide an advantage over subcutaneously administered insulin that is currently the state of the art, beyond the benefit of ease of administration, pain-free administration, and the potential for improved patient compliance. Because subcutaneously administered insulin is delivered peripheral to the GI tract and portal vein, and absorption of large biomolecules from the subcutaneous space is generally more prolonged, the first-phase insulin response is not well-replicated by subcutaneous insulin administration. By administration of the oral insulin formulations of the present invention, the plasma levels of insulin that occur upon the first (acute) phase of insulin secretion by the pancreas can be simulated by rapid, direct absorption from the GI tract.
In normal physiology, first-phase insulin secretion takes place 5 to 20 minutes after the start of a meal, and this effect has a well-known impact on prandial glucose homeostasis. The first phase of insulin secretion, while of short duration, has an important role in priming the liver to the metabolic events ahead (meal). The loss of first-phase insulin secretion is a characteristic feature of Type 2 diabetic patients in the early stages of the disease, and it is also observed in prediabetic states, namely individuals with impaired glucose tolerance. In the absence of first-phase insulin secretion, the stimulatory effect of glucagon on gluconeogenesis is not suppressed and may contribute to the development of prandial hyperglycemia. In the basal state as well as in the prandial phase, plasma glucose concentrations are correlated with hepatic glucose output. Therefore, restoration of first-phase insulin secretion at the time of meal ingestion should suppress prandial hepatic glucose output and subsequently improve the blood glucose profile.
Several approaches have been undertaken to prove this hypothesis. However, the therapeutic regimens were either too dangerous for a long-term treatment (such as intravenous administration of regular human insulin) or pharmacologically unsuitable (fast-acting insulin analogues). In addition, restoration of first phase insulin response appears to be difficult in patients with a long-standing history of diabetes who have lost most or all of their endogenous insulin secretion capacity. Furthermore, certain short acting insulin formulations, because of the speed with which the insulin provides a blood glucose lowering effect, may, between the time of administration of insulin and the time of ingestion of the meal, contribute to a lowering of blood glucose to a level that could range from subclinical hypoglycemia to more undesirable effects.
The rapid onset and the short duration of action of oral Insulin/4-CNAB following single dose administration in humans suggests that oral Insulin/4-CNAB may be well-suited for supplementation of first phase insulin secretion in subjects with type 2 diabetes. In a previous study, as set forth in International Patent Application No. PCT/US04/00273, patients with type 2 diabetes were administered a single doses of Insulin (300 U)/4-CNAB (400 mg) at or shortly before bedtime. Substantial decrease in insulin, C-peptide, and fasting blood glucose levels were observed. Insulin sensitivity, as assessed with the HOMA-model, was also significantly improved. This suggests that even a short-term treatment with pre-prandial Insulin/4-CNAB may be able to improve insulin sensitivity and, thereby, metabolic control.
It is, therefore, desirable to provide a pharmaceutical compositions of insulin that can be administered closer to as meal than previously known and to provide a protocol for insulin treatment for patients with impaired glucose tolerance or with early stage or late stage diabetes, which treatment can be administered orally multiple times daily, such as at or shortly prior to mealtime and/or at or shortly prior to bedtime, has a short duration of action, and has positive and long lasting effects on the patient's glucose tolerance, glycemic control, insulin secretory capacity and insulin sensitivity, but does not increase the risk of hypoglycemia, hyperinsulinemia and weight gain that are normally associated with insulin therapy treatments.